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I have built, installed my custom kernel. I need to prove that the new kernel is built and running. I have tried exploring /var/log/ for the log messages. I searched Xorg.log and dmesg.log and boot.log files for getting information about my newly built kernel, but I am unable to find the logs for the same. Can anyone let me know how and where I can find the logs for my new kernel. I am using ubuntu.

Thanks.

gst
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    check `uname -r`. It will indicate the version of your custom kernel. – brokenfoot Apr 21 '14 at 06:21
  • For log files refer http://stackoverflow.com/questions/13189576/getting-linux-kernel-debug-information-after-kernel-crash/13190359#13190359 – Jeyaram Apr 21 '14 at 06:22
  • is there anyway to get logs for the old and new kernel together, so that both of them could be compared based on the custom configuration? – gst Apr 21 '14 at 06:23

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You can get the kernel version by running uname -a. If you built your new kernel with a unique version name (I don't recall off hand where the setting is in the kernel configuration), it'll be obvious which kernel you're running.

user3553031
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  • is there anyway to get logs for the old and new kernel together, so that both of them could be compared based on the custom configuration? – gst Apr 21 '14 at 06:41
  • What sort of logs do you want? You could try booting one kernel, run `dmesg > kernel1.log`, then boot the other kernel and run `dmesg > kernel2.log` and compare the two logs. – user3553031 Apr 21 '14 at 06:51
  • By default my newly built kernel is running. I do not see any option for running my old kernel in ubuntu, as compared to fedora where I used to get options for selection of the kernel. – gst Apr 21 '14 at 06:57
  • can you use grub-customizer `sudo apt-get install grub-customizer` to see if your older kernel is still present? You could select the older version of the kernel as the default boot option in the second tab of grub customizer, save your changes, and then reboot. this should give you the logs for the older kernel. Once that is done you can compare the two logs. – Shehbaz Jaffer Apr 21 '14 at 07:51
  • @ShehbazJaffer. I have installed the grub-customizer and able to see the options as in the picture I am attaching with the question. Kindly guide me as to what I can further do. – gst Apr 21 '14 at 16:05
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@user2559758 you need to go into General Settings tab and select the older kernel version as the default Kernel. (there is a drop down menu, choose your old kernel as default kernel). Now save your changes (top left corner). exit grub loader. reboot. Once the reboot happens, cp /var/log/dmseg ~/oldlog. Again run grub-customizer switch to General Settings (2nd tab) choose new kernel version, save, reboot. Now you can copy cp /var/log/dmesg ~/newlog . Now do

diff oldlog newlog

Let me know if you have issues. If the answer is still unclear, please send the screenshot of General Settings tab. Also give the name of new and old kernel version names and I will be able to assist you better.

Shehbaz Jaffer
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